Is it possible to use a multiplexer to control the relays
By cycling thru the channels and providing the power
Needed for a relay thru the multiplexer's common.
It would be possible but absolutely stupid to use single dimension multiplexing to control any output. You get all the hassle of refreshing with absolutely zero advantage.
Is there a better yet simple way to do this?
There are lot and lots of better ways. Shift registers, latches, port expanders.
Is it possible to use a multiplexer to control the relays
By cycling thru the channels and providing the power
Needed for a relay thru the multiplexer's common.
It would be possible but absolutely stupid to use single dimension multiplexing to control any output. You get all the hassle of refreshing with absolutely zero advantage.
Is there a better yet simple way to do this?
There are lot and lots of better ways. Shift registers, latches, port expanders.
Wouldn't it save power usage?
Using A shift register i must provide the power
To all relays combined, in my case i may multiply the relays to 64 in the future.
Yarash:
So i wonder if looping thru the 8 channels very fast
Could keep the relays on constantly?
Relays may not tolerate high frequency AC drive, you'll get significant iron losses
(relay cores are soft iron rather than silicon steel laminate).
Furthermore you'd have to drive them at much higher voltage to get the right
average current, and your multiplexer wouldn't take that.
The correct approach is to use something like a 74HC595 shift register (which latches
output states) and have a drive circuit for each relay (presumably NPN transistor
and flyback diode. ULN2803 provides 8-channels of such drive, so a 595 and 2803
together would be a common choice. Check the voltage and current specs of your
relays of course.
Yarash:
So i wonder if looping thru the 8 channels very fast
Could keep the relays on constantly?
Relays may not tolerate high frequency AC drive, you'll get significant iron losses
(relay cores are soft iron rather than silicon steel laminate).
Furthermore you'd have to drive them at much higher voltage to get the right
average current, and your multiplexer wouldn't take that.
The correct approach is to use something like a 74HC595 shift register (which latches
output states) and have a drive circuit for each relay (presumably NPN transistor
and flyback diode. ULN2803 provides 8-channels of such drive, so a 595 and 2803
together would be a common choice. Check the voltage and current specs of your
relays of course.